Microscopic Examination and Sexual Assault Essay Example

Introduction

Microscopic examination is done to confirm the presence of spermatozoa for any area showing positive Acid phosphatase test. Also, if a sample from the physical examination had wet semen, then the sample can be observed microscopically to confirm the presence of spermatozoa (Chen and Hortin, 2000). If several samples were used and they indicated possible semen presence, then one can use the sample that shows most intense color change. However, if there is a likelihood of more than one sperm donor, then each sample must be used (ASCL, 2018).

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The suspect sample stain is cut and placed on a microscope slide. Then, the addition of two drops of de-ionized water is done, and the sample teased apart. Heat-fixing of the sample on the slide is then done over a hot plate. Application of Kernechtrot stain follows which is then drained from the slide after 15 minutes and Picroindorcamine stain addition is immediately for no more than 15 seconds (Dinis-Oliveira et al., 2010). The stain is then washed using methanol and the slide left to air dry. Once dry, 1-2 drops of Permount is applied, and a coverslip added (Koppl, 2005). The slide is observed under 200X or 400X for the presence of spermatozoa. If more than one slides were prepared from a sample and microscopy showed negative results for the presence of spermatozoa, RSID test shall be done for those areas where slides had no sperm. Presence of spermatozoa is a confirmatory test for semen/sperms in the sample thus sexual contact (Gunn, 2011).

RSID-Semen Test

If there is still enough sample, a stain is cut and placed in a test tube to which 1ml of a Universal buffer is added. More than 15 minutes is dedicated to extraction, and then 100 L of the extract is added to a sample well on RSID card (Dinis-Oliveira et al. 2010). Two red lines, one at 'C' and another at 'T,' appearing at the test window before 10 minutes confirm the presence of semen (Li, 2015). Lack of a red line at 'T' area is a confirmation of the negative result. A line must appear at the 'C' area otherwise the test is repeated, or the results are said to be inconclusive (Thompson, 2006). For negative results, serial dilution of the sample is done and the test repeated 13 (Chen & Hortin, 2000). If the results remain the same, then it is confirmed no semen is present in that sample (Dr. Imran, 2002).

Individualization: DNA Profiling

Confirmation of the presence of semen and spermatozoa may not necessarily confirm the suspicion of sexual assault. For identification, the sample stain is run through a DNA profiling and compared to the suspect.

Murder Weapon Examination and Collecting a Sample for DNA Test

Searching and examining a knife as a potential murder weapon has a potential to yield considerable information (Crouse & Vincek, 1995). Blood type of the victim, skin calls and fingerprints can potentially be found on the knife either at the sharp edges, the pointy end or the handle (Abi, 2010). On receiving a potential murder weapon (knife), one should examine it for visual identification of blood (Zachova, 2004). If present, the blood stain will be able to give information such as the victim's blood type (Koppl, 2005). The blood stain can also provide information on whether the victim was stabbed or cut depending on the pattern and location of the stain (Zachova, 2004). The use of luminol enables one to see Non-visible blood stains (Saks et al. 2003). Such blood stains collection is by use of sterile cotton wool dipped in distilled water. The cotton wool is used to rub the stain and extract blood sample which can be later used for blood typing and DNA analysis (Virkler & Lednev, 2009).

Examining the knife will indicate the presence of fingerprints on the handle. The possible types of fingerprints to find on the knife handle are latent fingerprints and patent fingerprints. Latent prints are left when palmar surfaces of the hand come in contact with a surface (Li, 2015). Blood on the knife handle leaves patent prints when held by hand (An et al. 2012). Fingerprints are best examined using an Alternate light source (Briody, 2005). This light emits light with a wavelength able to help visualize the prints. Examination by these light sources enables one to use photography as a record of the print image for further analysis. Fingerprints can also be by other methods such as chemical processing, fingerprint powder, and cyanoacrylate (Abi, 2010). Searching and examination of Touch DNA are done by use of a tape, swabbing with Q-tip or by scraping (ASCL, 2018). Touch DNA from epithelial cells left behind when a person comes in contact with an object (Dror, 2013). The cells will provide the DNA profile to identify or exonerate a suspect. It's only a few cells that are required to find touch DNA (Saks et al. 2003, 90; DNA Forensics 2018).

Trace Materials in Ski Masks

Locard's exchange principle postulates that whenever two or more objects come together, there is an exchange of trace materials. Such trace materials include fibers, hairs, touch DNA, and others such as saliva (Chewning et al., 2008). This trace materials form a significant part of the evidence in court cases and can be the difference between a suspect walking free or being guilty. Fibers can give information on where it has been. Hairs, saliva, and touch DNA are usually left on the mask when putting it on or removing it (Carey & Mitnik 2002).

Hair

Hair is one of the most common pieces of evidence commonly found in crime scenes. Crime scene hair consists of either the telogen phase or anagen phase. Anagen phase comprises active growth. It involves living cells and is likely to contain root tissue (Gefrides & Welch 2011).. These type of hair is mostly shed in violent and traumatic events (Cartmell & Weems, 2001). Telogen phase hairs are the most found in crime scenes (Girdler and Lednev, 2009). Telogen hair is hair in the resting phase and lacks living cells due to lack of root tissue (Dinis-Oliveira et al. 2010). The hairs shedding is natural thus can place a particular individual at a crime scene. Mitochondrial DNA from the telogen hair is analyzed (Lee & Harris, 2011). However, mitochondrial DNA is inherited maternally; therefore, it cannot discriminate maternal relatives (Kassim et al. 20...